The pancreas is a large gland located behind the stomach and close to the duodenum. It secretes digestive enzymes that enter the small intestine via a duct. These enzymes facilitate the digestion of proteins, fats and carbohydrates. In addition to the digestive enzymes the pancreas also releases insulin and glucagon, which play an important role in sugar metabolism.
Pancreatitis is a disease in which the pancreas becomes inflamed. Damage to the pancreas occurs when digestive enzymes are activated and begin attacking the gland. In severe cases, there many be bleeding into the gland, tissue damage, infection and cyst formation. There are two forms of pancreatitis. An acute form which occurs suddenly and may be life threatening. A chronic form of pancreatitis may arise if the patient persists in drinking alcohol, which results in the reduction of pancreatic function and severe pain and weight loss. There are approximately 50,000 to 80,000 cases of acute pancreatitis in the United States each year. It is more common in men than in women.
Currently, diagnosis of pancreatitis is difficult. Usually pancreatic function tests help the physician determine if there are enough pancreatic enzymes being made. CAT scan can determine if there are abnormalities in the gland itself, such as gallstones, which are frequently associated with this disorder. As chronic pancreatitis is a leading risk factor for pancreatic cancer, it should be treated as soon as the diagnosis is made.
The pancreas is comprised of about 80% acinar cells, 1%–2% islet cells and 10%–15% of cuboidal ductal cells. Acinar cell carcinoma accounts for 1%–2% of pancreatic carcinoma, with an additional 10%–15% of pancreatic carcinoma comprised of acinar cells and other cell types [Nomura et al., Ultra. Path. (1992) 16:317–329]. All of the causes of acute pancreatitis affect the acinar cells in a way that results in the activation and retention of the digestive enzymes, which injure the acinar cell and cause the release of cytokines. The cytokines attract inflammatory cells, especially neutrophils, leading to further secretion of cytokines. It is proposed that the released inflammatory molecules induce pancreatic edema, and local necrosis. Certain studies have suggested that cytokine inhibtors may improve the course of pancreatitis in specific clinical settings.
Interleukin-22 (IL-22) is a newly identified cytokine produced by activated T cells and is related to interleukin-10 (IL-10). IL-22 signals through a receptor complex comprised of CRF2-4, also known as IL-10Rβ, and a new member of the class II cytokine receptor family, interleukin-22 receptor (IL-22R) [Xie et al., J. Biol. Chem. (2000) 275, 31335–31339]. Of the members of this receptor complex, IL-10Rβ is expressed in several tissues while the expression of IL-22R is fairly restricted, with high expression in the pancreas, suggesting that IL-22R is controlling the site of action of IL-22. As an example, murine IL-22 induces changes in gene expression in pancreatic acinar cells of several genes including pancreatitis associated protein (PAP1), a gene overexpressed in acute pancreatitis [Iovanna et al, J. Biol. Chem. (1991) 266, 24664–24669]. IL-22 signaling through a receptor complex that is highly expressed in pancreas, suggests that IL-22 may modulate an immune/inflammatory response in the pancreas, and may be involved in diseases of the pancreas including pancreatitis.